Endothelin is a cyclic peptide which possesses a strong, long-lasting vasoconstricting effect, and is thought to be one of the substances responsible for hypertension, asthma, cerebral apoplexy, angina pectoris, actute renal insufficiency, cardiac infarction, and cerebral vasospasm. Consequently, a substance which antagonizes endothelin and inhibits its effects is expected to be useful for the treatment and prevention of these diseases.
It is known that the cyclic peptide represented by the following formula (A) exhibits the endothelin antagonism (Japanese Published Unexamined Patent Application No. 130299/91): ##STR1## (wherein U represents D-Val or D-allo-Ile, R.sup.A represents hydrogen or an amino-protective group, and R.sup.B represents hydrogen or a carboxy-protective group). Related cyclic peptides BE-18257 derivatives and BQ-123 derivatives have also been reported (Japanese Published Unexamined Patent Application No. 94692/91, U.S. Pat. No. 5,114,918). ##STR2##
Cyclodepsipeptides represented by the following formula have been reported as cyclic peptides containing abnormal amino acid [Cochinmicins; J. Antibiotics, 45, 1709-1722 (1992)]. ##STR3##
______________________________________ Cochinmicin X * ______________________________________ 1 I H R 2 II Cl S 3 III Cl R ______________________________________
Olygopeptides represented by the following formula have also been reported as other peptides having the endothelin-antagonizing activity [EP-A-0457195, J. Pharm. Exp. Ther., 264, 1040-1046 (1992)]. ##STR4##
The similar peptides represented by the following formula have further been reported (Abstract of the 65th Conference of Biochemical Society of Japan, p 769) ##STR5##
There have been many reports on endothelin derivatives and partial peptides of endothelin [WO91-13089, Japanese Published Unexamined Patent Application No. 59098/93, WO 92-02237, J. Med. Chem., 35, 3301-3303 (1992), Biochem. Biophys. Res. Commun., 179, 286-292 (1991), Biochem. Biophys. Res. Commun., 184, 953-959 (1992), FEBS Lett., 311, 12-16 (1992), Biochem. Biophys. Res. Commun., 184, 100-106 (1992), Biochem. Biophys. Res. Commun., 183, 566-571 (1992), Proc. Natl. Acad. Sci. U.S.A., 88, 7443-7446 (1991), J. Pharm. Exp. Ther., 260, 632-636 (1992), EP-A-499266, etc].
There have also been reports on random modification of C-terminal peptides of endothelin-1 [BioMed. Chem. Lett., 3. 497-502 (1993), BioMed. Chem. Lett., 3, 519-524 (1993)].